In turbines, particularly in and around turbine sections of turbines, turbine parts, such as casings, are exposed to a hot working fluid of the turbine. Hence, cooling systems are applied for cooling the turbine parts.
For cooling purposes, cooling air systems are installed for providing a cooling air stream to the hot turbine parts. The space for installing a cooling air system and for providing effective cooling on the outside and inside of the turbine parts, such as casing parts, is limited. Furthermore, complex cooling systems are expensive and the reliability is low. Moreover, a high amount of cooling air may affect negatively the turbine performance.
EP 0 578 639 B1 discloses a turbine casing. The turbine casing is partially enclosed by a cowling so that a gap is defined between the turbine casing and the cowling for the flow of cooling air.
U.S. Pat. No. 4,841,726 discloses a gas turbine jet engine of multi-shaft double-flow construction. A front compressor or fan supplies in the gas turbine compressed air into a secondary channel which is arranged coaxially to the propulsion unit axis and which is formed between outer and inner wall structures from which a secondary air component is taken and blown out against the turbine housing structures for the purpose of cooling. The secondary air channel extends essentially over the entire propulsion unit length or at least up to the area near the turbine housing structure while the secondary air component is taken off from the secondary flow by way of openings in the inner wall structure which are arranged in direct proximity of the respective turbine housing structure.
U.S. Pat. No. 4,242,042 discloses a temperature control of an engine case for clearance control. The injection of cooling air into an annular space is defined by a double wall construction consisting of the case and an outer air seals serve to control the leakage in and out of the space and the temperatures of the engine case. The temperature range between the hot gas stream and the cool air acting on the engine case controls shrinkage and expansion of the case which in turn positions the seal relative to the tip of the rotating blades, which can be manifested as a function of engine power or other parameters.
US 2004/0018081 A1 discloses a low pressure turbine casing with a conical annular shell circumscribed about a center-line. A forward flange is positioned to a forward end of the annular shell. A forward hook extends afterwards from the forward flange. First and second rails having first and second hooks, respectively, extend afterwards from the annular shell. First and second cooling holes extend through the first and second rails, respectively. Cooling air feed holes extend through the forward flange. The first and second cooling holes are radially disposed through the first and second rails, respectively, with respect to the centerline or disposed through the first and second rails at an oblique angle with respect to the centerline. A low pressure turbine casing and a shroud assembly further includes a first annular cavity in fluid flow communication with the first cooling holes and the second cooling holes.
GB 2 108 586 discloses a clearance control between tips of turbine rotor blades and the surrounding casing. Cooling air may be directed through a line to a low pressure turbine casing.
U.S. Pat. No. 6,227,800 B1 discloses a turbine casing which supports a row of nozzle vanes through hot combustion gases may flow. A baffle surrounds the casing to define a cooling duct. A nacelle surrounds the turbine casing to define a bay having an inlet for receiving bay air, and an outlet for discharging the air. The cooling duct includes an inlet which receives the bay air for flow along the turbine casing for selective cooling thereof.
U.S. Pat. No. 6,625,989 B2 discloses a method and an apparatus for the cooling the casing of the turbines of jet engines, in which cooling air is diverted from a bypass flow and supplied to the outer side of the casing via an inlet duct provided with a shut-off element. The cooling air is supplied to a first chamber in which it is divided by volume. One portion of the cooling air is issued to the casing via orifice holes, while another portion is ducted via several tubes to a second chamber which annularly encloses the casing in the area of a low-pressure turbine.
EP 0 618 349 A1 discloses a turbine assembly for a gas turbine engine which comprises alternate annular arrays of rotor blades and stator vanes enclosed in an annular casing. Each stator vane is secured by a platform at its radially outer extent. A bolt extends through a flange on the platform to locate the stator vane relative to the casing and prevents any circumferential movement of the stator vane. The bolt extends radially through the casing to engage an annular cooling duct. The annular cooling duct encloses the casing to define a cavity through which in operation cooling air passes to cool the casing.